AD 269-2: Following guidance is based on the guidance given in AD269
For optimum economy, liaison is required between the structural engineer responsible for the design and the fire protection supplier. This is particularly important when an intumescent coating is to be applied to beams with large web openings. It can be economically very important to take account of the level of loading on different parts of the beam. Cellular beams in which the utilisation factors for normal design are significantly below unity require less protection than more highly stressed beams.
The SCI recommends one of the following options for design of beams with circular web openings, protected using an intumescent coating. The option selected will depend on the amount of design information available and whether evidence of performance in fire tests is available.
The simple use of the tabular information contained in AD269 has been withdrawn and SCI now recommend that the revised information contained in RT1085 is followed.
Readers should be aware that product-specific versions of the design information contained in RT1085 will start to become available as manufacturers start to use the new testing and assessment protocol.
Design software that explicitly calculates the load carrying capacity for beams with web openings at the fire and ultimate limit states may be used. The development of such software should be based on the observed temperature distribution throughout the beam for different coating thicknesses and the observed performance of the beam in loaded fire resistance tests.
The thickness may be assessed using a structural model based on the principles given in EC4-1-2. The model should take account of the increased temperatures of the web posts relative to the flanges. Information on temperatures may be obtained from fire tests.